Undergraduate thesis, Institut Teknologi Sepuluh Nopember. Mikroalga merupakan salah satu sumber alam yang berpotensi dalam pembuatan biodiesel karena mengandung minyak yang cukup tinggi. Mikroalga merupakan organisme tercepat dalam fotosinstesis sehingga memiliki produktivitas yang tinggi. Dalam penelitian ini, jenis mikroalga yang digunakan yaitu Chlorella sp. Tujuan dari penelitian ini yaitu mempelajari pengaruh variasi biomassa:pelarut, kosentrasi katalis, daya microwave, waktu reaksi dan penambahan co-solvent terhadap yield biodiesel yang dihasilkan, mengetahui kondisi operasi optimum pada proses pembuatan biodiesel serta mengetahui komponen dan karakteristik dari produk biodiesel yang dihasilkan.
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The fatty acid methyl ester FAME production from Chlorella vulgaris has been studied by sequential investigation such as microalgae culturing, lipid extraction, and lipid conversion to FAME. The C. The optimum of dry cell biomass as The area was corresponded to FAME output as Optimization of the transesterification reaction will be developed in future to improve the FAME product. Depletion of petroleum energy resources or fuel oil as a result of high fuel consumption becomes a major issue in many countries.
To overcome this problem many countries develop biofuels, one of which is biodiesel as renewable energy. It is also classified as a safety energy, because it has no aromatic compounds, easily degraded, and free of SOx component.
Biodiesel is more specifically defined as the monoalkyl esters of long-chain fatty acids derived from the chemical reaction transesterification of renewable feedstocks, such as vegetable oil or animal fats, and alcohol with or without a catalyst [ 1 ]. Biodiesel has a significant energy similar to petroleum-derived diesel oil, therefore it has more potential to substitute the diesel. Microalgae has been suggested as a good candidate for fuel production because of their advantages of higher photosynthetic efficiency, higher biomass production and faster for growth than other energy crops [ 3 ].
Microalgal cells have a high oil content, so it is a suitable to be developed as a material source in the biodiesel production. The composition of various fatty acids in microalgae makes the biodiesel that has different characteristics [ 2 ].
In addition, the use of microalgae does not compete with food [ 3 ]. Indonesia has a high biodiversity of microalgae scattered in terrestrial and marine waters, however the potency of microalge has not yet explored optimally. Microalgae consist of various species such as diatom microalgae Bacillariophyceae , green microalgae Chlorophyceae , gold microalgae Chrysophyceae , and blue microalgae Cyanophyceae [ 1 ].
Microalgal cultivation is essential for the provision of sustainable feedstock sources in biodiesel production. Microalgal cultures can be performed in a bioreactor containing a liquid medium with additinal supply of air and irradiation.
The cost of cultivation is also relatively cheap, since it does not require much fertilizer and nutrients. The main components of triglycerides in microalgae can be converted to biodiesel or fatty acid methyl ester FAME through the transesterification reaction with methanol by using acid, base or enzyme catalysts.
The reaction can be run in two ways, i. In the ex-situ method, the biodiesel is prepared through two stages, started by lipid extraction then followed by a transesterification reaction. While in the in-situ method, both lipid extraction and transesterification steps are performed in one process. One of key parameters required for FAME production with ex-situ process is the high availability of lipid. Solvent extraction is used to obtain lipid from microalgae due to its simplicity and relatively inexpensive process which has almost no investment for equipment [ 6 , 7 ].
Various solvents such as hexane, methanol, chloroform, and combination of them are usually used in the extraction [ 8 ]. The efficiency on lipid extraction is highly dependent on the polarity of the solvent and the ease of solvent access to the lipid storage in the cell parts. In addition to the solvent extraction, some methods which facilitate the cell disruption are usually combined to enhance the lipid yield by some pre-treatments such as microwaves, sonication, bead-heating and supercritical extraction with CO 2 [ 9 , 10 ].
The most efficient method for extracting compounds from several species of microalgae including C. The superiority of the sonication method in lipid extraction has been widely reported in several references, which can reduce on the sample extraction times [ 23 , 24 , 25 ]. The sonication can disrupt microbial cells through a cavitation effect, because it produce high-energy microscopic bubbles along with mechanical pressure and shear [ 23 ].
Moreover, It has increased lipid extraction from vegetal tissue through the action of accelerating rehydration or swelling of plant cells accompanied by tissue matrix fragmentation, accompanied by mass transfer and penetration of the solvent into the cell and the release of cell contents into the solvent [ 23 , 24 ]. Based on this principle, then the ultrasonication is applied to assist the lipid extraction from Indonesia strain of Chlorella vulgaris microalgae as an effort to get a high yield of lipids.
The comparison of lipid from the microalgae is also still unknown, so it is very interesting to be studied. All chemicals for solvents and reagents were obtained from commercial sources and had a specification in analytical grade. The culture was incubated under aerated CO 2 at room temperature. The cell density of culture was measured by spectrophotometry at nm to determine the growth curve.
Lipid extraction was performed by using the Bligh and Dyer method [ 12 ]. The 5 g of dry biomass of C. After centrifuging at rpm for 10 min, the solvent phase was taken and evaporated in the rotary evaporator under vacuum at 60 o C. This work was repeated for three times to get the entire lipid. The effects of solvents polarities on lipid extraction was also investigated in this study. Yield of lipid was calculated based on the equation:. The ex-situ transesterification was performed according to the Zhang method [ 13 ].
The reaction was run at 45 o C for 2 h. The filtrate was collected and added 10 mL n-hexane. The mixture was centrifuged at g for 20 min.
Two layers which formed after centrifugation was shaken out for 20 min in the separation funnel. The botton layer containing hydrophilic phase was removed, whereas the top layer containing organic phase was taken and washed with 10 mL of hot water.
A solution containing FAME was collected and its weight was measured. Injection and detector temperature were maintained at o C. The MS Source and Quard of the instrument were o C and o C, respectively, then set at low mass of 30 and high mass of for sample measurement.
Methyl heptadecanoate was used as standard for this analysis. The conversion of biodiesel resulting from the transesterification process is determined by the equation:. The growth of microalgae in BG medium with an inoculum showed typical pattern with 4 phases consisting of adaptation, logarithmic, stationary and death phases Figure1.
The adaptation phase was occured at day marked by no significant growth, because the microalgae need initial adaptation to new environment.
The logarithmic phase was occurred at day 1 — 5 that indicated by a significant increase in the growth of C. At days 5, the growth of C. In this phase, the cell number of growth and death is balance. Characteristics and morphological feature of the local strain of C. The individual cells of the strain are green colour, unicellular, spherical in shape its shows the Figure 2.
Preparation of C. A dry biomass of The growth curve of Chlorella vulgaris in BG medium. The curve showed a doubling time for cell growth on 3.
Citation: Open Chemistry 17, 1; The lipid from C. The effect of ultrasonication power and polarity of solvents on lipid extraction was investigated in this study.
The solvent of n-hexane extracted lipid higher than the methanol, and a mixture chloroform with methanol. It seems that n-hexane has a role to disrupt the existing hydrophobic interactions between non-polar and neutral lipid compounds. Hexane has a higher selectivity for non polar lipid than methanol and chloroform. It can partitions preferentially to the center of the lipid bilayer with a favorable entropy change, so this consistent with the hydrophobic effect [ 25 , 27 ].
Similar result was obtained by Krishna et al. The ultrasound-assisted extraction can increase the extraction efficiency through cavitation and some mechanical effects. Cavitation can disrupt microalgae cells then facilitate the lipid becoming easy to contact with organic solvent.
Another mechanical effect caused by ultrasound may also be the agitation of the solvent used for extraction, thus increasing the contact surface area between the solvent and targeted compounds by permitting greater penetration of solvent into the cells [ 28 ]. Because of the cavitation role is affected by the solvent factor as solvent viscosity and surface tension [ 26 ], so the choice of precise solvent is needed.
The rise of lipid yield in n-hexane is higher than other two solvents. The n-hexane might support well the cavitation role of ultrasound so it could disrupt the microalgae cells optimally. Since the presence of lipids in cells is enclosed by polar phospholipid layers of cell membrane, the splitting of the layer is required to release the non-polar lipids [ 13 ].
Based on this principle, the lipid extraction in the study was also conducted by using a mixed solvent of n-hexane - ethanol and n-hexane - methanol in various ultrasonication power. Although an increase in the power ultrasonicator can improve the cavitation process so the cell is easy to lysis, but if the power used is excessive, it can cause bubbles that actually reduce lipid yield.
The yield of lipid extraction with binary solvent of n-hexane-ethanol in various ultrasonication power. For this result showed that an increase in lipids extraction yields was obtained when non-polar and polar solvent mixtures were used.
The use of polar and non-polar solvent combinations is enabled so that all lipids in both neutral and polar lipids can be extracted properly. The non-polar organic solvents is inadequate used to disrupt the membrane—lipid—protein associations, due to weak interactions to the complex.
However, polar organic solvents can break the lipid—protein associations by forming hydrogen bonds with the polar lipids in the complex [ 29 ]. Ethanol has a polarity index lower that ethanol [ 25 ], so the mixing of ethanol into n-hexane produce a mixed solvent with a lower polarity index than if n-hexane is mixed with methanol. However the polarity of mixed solvent of n-hexane — ethanol that formed might facilitate an optimal cavitation role for C. The lipid product for the extraction was analyzed by GC-MS to search the fatty acids component, and resulted pentadecylic acid, palmitic acid, heptadecanoic acid, stearic acid, margaric acid and nonadecylic acid as component of the lipid Table 1.
The production of fatty acid methyl ester FAME is conducted by mixing lipid with methanol in transesterification reaction using H 2 SO 4 catalyst. The glyceride that presented in the lipid is transformed to glycerol and methyl esters. Because of the transesterification is included in the reversible reaction, so the excessive of methanol is needed to shift the reaction toward the FAME product [ 16 ].
Methanol was chosen as a reactant in the study because it is classifed as a cheap material, having a low boiling point and its excess in the glycerol phase easily to be separated [ 15 ].
Fatty acid profiles analyzed by GC-MS showed The area is corresponded to FAME rendement as The major peaks of fatty acids found in Chlorella vulgaris were palmitic acid C , stearic acid C and margaric acid C , and nonadecanoic acid C For fuel properties, the length of carbon chain and the number of double bonds are important, in which C and C are the ideal biofuel feedstock [ 17 , 18 ]. Five common feedstocks includes C palmitic acid , C stearic acid , C oleic acid , C linoleic acid and C linolenic acid which were suitable for biodiesel production [ 19 , 20 ].
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Template Tools. Penelitian ini bertujuan untuk mempelajari keragaman spesies mikroalga dari perairan Danau Kerinci di Jambi, menganalisis kandungan lipid dan asam lemak isolat mikroalga. Mikroalga diisolasi dengan kombinasi teknik goresan, pengenceran berseri, dan mikropipet. Penentuan tingkat pertumbuhan dengan spektrofotometer UV-Vis.
OPTIMASI PROSES PEMBUATAN BIODIESEL DARI MIKROALGA CHLORELLA SP
The fatty acid methyl ester FAME production from Chlorella vulgaris has been studied by sequential investigation such as microalgae culturing, lipid extraction, and lipid conversion to FAME. The C. The optimum of dry cell biomass as The area was corresponded to FAME output as Optimization of the transesterification reaction will be developed in future to improve the FAME product.